Emperor of Rome from 284 to 305. He distinguished himself in the Persian War and was chosen emperor by the army. As the empire was unwieldly and exposed to attack, he associated with himself Maximian, with whom he celebrated the last triumph in Rome, 20 November303, and further distributed his power by granting the inferior title of Cæsar to two generals, Galerius and Constantius Chlorus. During the greater portion of Diocletian’s reign, Christians enjoyed peace and prosperity, but under the influence of Galerius he inaugurated, beginning in 303, the last and most terrible of the ten persecutions of the early Church, which was waged with greatest severity in the East.